Many courier companies provide the service of delivering packages on behalf of their customers. In exchange for delivering packages to the customer's specified destination, the courier company charges a fee. Typically, the fee is based upon one or more of (1) the size of package, (2) the weight of the package, (3) the destination of the package, and (4) the time within which the package must be delivered.
A problem exists in determining the appropriate charge for delivering the package. In some cases, the volume of the package is the limiting constraint, especially for goods shipped by overnight carrier. In other circumstances, the package's weight can be the limiting factor. What is needed is a way of measuring such physical parameters of a package to evaluate the appropriate shipping charge for the customer.
For large courier companies, these charges need to be determined for a very large number of packages. Large courier companies typically have central sorting stations. In these sorting stations, packages picked up from customers are processed for delivery to the customer's specified destination. Typically, in such circumstances, packages will be unloaded onto a conveyor belt, and the volume and/or weight of each package will be determined as the package moves along the conveyor belt. The customer is automatically billed later. Such a system is disclosed in published U.S. patent application No. 20030225712.
In other situations, there is a lower volume of packages, and payment for shipping is typically obtained at the time the customer provides the package to be delivered. For example, there are many companies that offer private mailbox services and the like, in a storefront setting. Typically, such companies also offer courier services. A customer enters the store with a package, and the package is sized and/or weighed immediately to determine shipping charges. In such cases, the measuring device used typically requires the user to place the package on a platform for measurement.
U.S. Pat. No. 4,773,029 (“Claesson”) discloses a measuring device for measuring three dimensions of an object being carried by a conveyor belt. The height of the object is measured by paired transmitters and receivers that are positioned on opposite sides of the conveyor belt, and are aimed across the conveyor belt. The width of the package is measured by paired transmitters and receivers that are positioned above the conveyor belt, and below the surface of the conveyor belt, between two sections thereof. The length of the device is measured by performing a calculation using the speed of the object on the conveyor belt.
The rows of transmitters and receivers are made up of modules. Thus, if the size of the relevant object is small, fewer modules can be used to create rows of transmitters and receivers. If, however, an object is larger, and more transmitters and receivers are required to measure its dimensions, then a greater number of modules can be used to extend the size of any set of transmitters or receivers.
The transmitters and receivers operate in pairs. Therefore, if a particular receiver is not receiving its signal from the particular transmitter from which it is paired, then the CPU will know that the object being measured is blocking the signal.
The system also has a calibration sequence which is performed after the measurement of each object, in anticipation of the next object. Specifically, the output of each receptor is measured to determine its raw output when it is receiving a signal from its corresponding transmitter, and when it is receiving no signal from its corresponding transmitter. A decision threshold for determining the presence of a signal, based on the raw output of each receiver, is calculated and stored in the computer for use with the next object.
There are a number of problems with this device. First, the necessity of pairing transmitters with receivers creates an unwieldy structure, in which transmitters or receivers must be positioned above the conveyor (thus taking up space and potentially blocking larger objects) and below the conveyor (thus inefficiently requiring a section break in the conveyor right at the measuring device). Also, the fact that each transmitter is positioned on the opposite side of the measuring platform from a corresponding receiver limits the size of the package that can be measured. In addition, the system uses a great deal of computing power, re-calibrating every signal receiver after each object is measured.
U.S. Pat. No. 5,878,379 (“Dlugos”) discloses a dimensional weighing apparatus entitled “Coarse Volume Measurement with Interlock”. The device includes a scale for weighing a package, together with a measuring frame having three axes. Along each axes are paired signal transmitters and receivers. The signal transmitters and receivers are positioned adjacent to one another, and oriented so that if the side of a package is positioned adjacent to the pair, then the signal from the transmitter will reflect off the package and travel to the receiver.
A substantial problem with the Dlugos device is that it provides only coarse measurements of package size. The device can only achieve limited precision based on the polling of these individual sensor pairs. So coarse are these measurements that the device includes an apparatus for indicating to the user that he requires a more precise measurement, which he is required to do manually.